Double-Clutch Transmission Upshift Control via Drag Torque
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Solution Overview
Problem
Dual clutch transmissions face challenges in optimizing switching sequences, particularly during multiple upshifts, where synchronization times are lengthy and wear on friction clutches is high due to high differential speeds.
Innovation Solution
A method for controlling double upshifts in dual clutch transmissions that involves intermediate clutching, where the differential speed at the target gear is reduced by applying a drag torque, which is built up gradually and terminated based on specific conditions, such as friction speed thresholds, to minimize wear and synchronization time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional direct synchronization method is used for upshifts, then the switching process is simple, but the synchronization time is lengthy and wear on friction clutches is high due to high differential speeds
Solution Approach 1:
The synchronization process is divided into multiple phases: initial clutch engagement, intermediate synchronization phase with reduced differential speed, and final gear engagement. This segmentation allows each phase to be optimized independently, reducing overall synchronization time while managing complexity through structured control steps
Solution Approach 2:
The friction clutch is engaged in advance before the target gear is fully synchronized, creating a preliminary connection that begins the synchronization process early. This preliminary action reduces the time required for full synchronization by overlapping the clutch engagement with the speed matching process
2Reliability
If traditional direct synchronization method is used for upshifts, then the switching sequence is simple, but wear on friction clutches is high due to high differential speeds
Solution Approach 1:
The clutch engagement is made dynamic rather than static, with the clutch slip ratio being continuously adjusted during the synchronization process. This dynamic control allows the differential speed to be managed optimally throughout the engagement, reducing wear while adapting to changing operating conditions
Solution Approach 2:
The differential speed parameter is actively changed during the synchronization process by controlling the clutch engagement timing and slip characteristics. By modifying this key parameter, the wear on friction clutches is reduced while achieving successful gear synchronization
3Reliability
If intermediate clutching with drag torque is applied to reduce differential speed, then wear on friction clutches is reduced, but the control process becomes more complex
Solution Approach 1:
The control system continuously monitors the differential speed between the input shaft and the target gear, using this feedback to determine when to engage the friction clutch and how much drag torque to apply. This feedback mechanism simplifies the control process by providing clear decision criteria rather than requiring complex predictive control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces synchronization times and wear on friction clutches by managing differential speeds, allowing for more efficient and shorter switching processes, especially during high-speed upshifts.
Implementation Method 1
applying a drag torque... built up gradually... terminated based on specific conditions, such as friction speed thresholds, to minimize wear
Data Source
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Figure 8
AI summary
The invention relates to a method for controlling a shifting-up process (e.g. 4-6) in a double-clutch transmission (10) which has a double-clutch transmission input shaft (12) which is connected to a drive engine (14), two friction clutches (16, 18) and two component transmissions (20, 22), having the steps: - sensing of a shifting request from a low source gearspeed (4) into a higher target gearspeed (6), wherein the source gearspeed and the target gearspeed are assigned to one (22) of the two component transmissions (20, 22) of the double-clutch transmission (10), - opening of the friction clutch (18) which is assigned to the one component transmission (22), and closing of the friction clutch (16) which is assigned to the other component transmission (20), in order to transmit, without a dip in the tractive force, driving power via an intermediate gearspeed (5) of the other component transmission (20), wherein, as a result, the rotational speed of the double-clutch transmission input shaft (12) is lowered, - disengagement of the source gearspeed (4) and intermediate pressing on the friction clutch (18), assigned to the one component transmission (22), before the target gearspeed (6) is engaged, wherein the rotational speed of the one component transmission (22) is reduced by the pressing operation by virtue of the fact that the double-clutch transmission input shaft (12) which rotates at a reduced rotational speed transmits a drag torque (58) to the one component transmission (22), with the result that it is possible to start synchronization of the target gearspeed (6) at a reduced differential rotational speed (w), and - opening of the friction clutch (16) which is assigned to the other component transmission (20), and closing of the friction clutch (18) which is assigned to the one component transmission (22), in order to transfer driving power to the target gearspeed (6) without a dip in tractive force.